Studies of human patients with brain damage have indicated that neural structures of the limbic system are mediators of the processes of learning and memory. The proposed studies are designed to contribute to an understanding of the basic mechanisms of learning, memory, and pathology of memory by studying selective (associative) unit activity in limbic structures, which accompanies discrimination learning and reversal in intact behaving animals. Past studies have revealed selective neuronal activity in several brain systems. The significant observation was that selective activity in each system bore a unique relationship to the overt behavior of the subjects, and to the learning task. The unique relationships provided information about the function in behavior and learning of different neural systems. Of particular interest was the observation that selective neuronal activity showed a progression from limbic cortex (AC) to limbic thalamus (AV) as the behavioral discrimination was acquired. This outcome suggested that limbic corticothalamic flow of selective neuronal activity was an essential reflection of the process of information storage in the brain. Major objectives of research proposed are: 1. to determine the generality of corticothalamic flow in learning by examining other limbic corticothalamic systems; b. to establish the behavioral relevance of selective neuronal activity of the AC-AV corticothalamic system; c. to describe the cellular basis of selective neuronal activity. An ultimate goal of the research is to identify behavioral functions of limbic neuronal populations and subsequently to reveal the neuroanatomical, pharmacological and morphological properties of the neurons in question.